Cardiovascular disease, including atherosclerosis, is a leading cause of death in the United States. One method for treating atherosclerosis and other forms of vessel lumen narrowing is angioplasty. The objective of angioplasty is to restore adequate blood flow through the affected vessel, which may be accomplished by introducing a treatment catheter within the narrowed lumen of the vessel to dilate it.
The anatomy of vessels varies widely from patient to patient. Often a patient's vessels are irregularly shaped, highly tortuous and very narrow. The tortuous configuration of the vessels may present difficulties to a clinician in advancement of a treatment catheter to a treatment site. In addition, in some instances, the extent to which the lumen is narrowed at a treatment site is so severe that the lumen is completely or nearly completely obstructed, which may be described as a total occlusion. A chronic total occlusion (CTO) is generally an occlusion that has completely blocked a blood vessel for an extended period of time.
The tissue composition of a CTO is generally a variable mix of collagen-rich plaque, layered thrombus, calcium, and inflammatory cells with fibro-calcific caps at both ends. This fibrous cap may present a surface that is difficult to penetrate with a conventional medical guidewire such that one method of crossing a CTO includes utilizing a stiffer guidewire to create a new channel through the occlusion. Due to the fibrous cap of the CTO, a stiffer guidewire still may not be able to cross it and the distal end of the guidewire may buckle or prolapse within the vessel when force is applied. In addition, a clinician must take care to avoid perforation of the vessel wall when using a stiffer guidewire.
By way of mere examples, CTOs are often defined as coronary occlusions that have had thrombolysis in myocardial infarction (TIMI) grade flow of 0 or 1 for an estimated duration of at least one month. Available interventional procedures to treat coronary occlusions include coronary angioplasty, e.g., percutaneous transluminal coronary angioplasty (PTCA), and stent placement, e.g., drug-eluting stent placement. These procedures are considered percutaneous because they are performed through a tube or catheter inserted into a blood vessel, rather than through an incision in the chest. However, coronary artery CTOs have historically been some of the most challenging types of blockages to treat with percutaneous interventional procedures because the fibrotic and calcified nature of the CTOs makes passage difficult. As a result, many patients with coronary artery CTOs require coronary artery bypass graft (CABG) surgery to treat the blockage. CTOs are also frequently present in many other locations of the human vascular system, including in peripheral vessels.
Therefore, a need exists to develop better systems and methods for percutaneous treatment of occlusions, especially with respect to improving the available systems and methods for penetrating and bypassing the occlusion or anatomical blockage, and for incorporating multiple options to recanalize the vessel within a single device.